What a lot of people fail to see in BA with respect to a large number of LH SFO's is that they have worn 4 stripes before and aren't really that fussed about which seat they sit in as the 'panacea' of a command is not a priority whereas lifestyle is.
It's difficult to go from the top of a structure where choice is king to the bottom of the LHS structure where you lose all control over your working hours again. Couple that with the nice tax man taking a large chunk of your earnings again over £100,000 and the incentive to move is lessened. This will only get worse as those pilots who are on the money purchase pension scheme don't need the last two years gross earnings as a Captain to 'top up' their NAP's/APS pensions.
However, changes to the pay system and the fixed flying pay have taken out the 'plum' trips structures and based line selection and trip selection purely on personal preference therefore opening up the entire route structure to everyone from the most senior to the most junior.
There is a growing undercurrent of feeling for removing the PP18 cap given the retirement situation and the over crew of ex-BMI captains as the cap is seen as unrealistic and unfair. However you only need to bid for any command, there is no guarantee you will get one.